#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H

#ifndef NULL
#define NULL ((void*)0)
#endif
/*container_of 通过结构体成员,获取结构体首地址*/
/*
    ptr:结构体成员地址
    type:结构体类型
    member:结构体成员
*/

#if defined(container_of)
#undef container_of
#define container_of(ptr, type, member) \
    ({                                                    \
        const typeof(((type*)0)->member)* __mptr = (ptr); \ /*typeof(((type*)0)->member) 获取ptr的数据类型,__mptr:保存ptr地址,之后用于推导结构体首地址*/
(type*)((char*)__mptr - offsetof(type, member));
\ /*offsetof:获取member在结构体内想对于首地址的偏移地址*/
})
#else
#define container_of(ptr, type, member)                   \
    ({                                                    \
        const typeof(((type*)0)->member)* __mptr = (ptr); \
        (type*)((char*)__mptr - offsetof(type, member));  \
    })
#endif

#if defined(offsetof)
#undef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) & ((TYPE*)0)->MEMBER)
#else
#define offsetof(TYPE, MEMBER) ((size_t) & ((TYPE*)0)->MEMBER)
#endif

#include <stddef.h>

/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:        the pointer to the member.
 * @type:       the type of the container struct this is embedded in.
 * @member:     the name of the member within the struct.
 *
 **/
#define container_of(ptr, type, member)                   \
    ({                                                    \
        const typeof(((type*)0)->member)* __mptr = (ptr); \
        (type*)((char*)__mptr - offsetof(type, member));  \
    })

struct list_head {
    struct list_head *next, *prev;
};

static inline void INIT_LIST_HEAD(struct list_head* list)
{
    list->next = list;
    list->prev = list;
}

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(
    struct list_head* new, struct list_head* prev, struct list_head* next)
{
    next->prev = new;
    new->next  = next;
    new->prev  = prev;
    prev->next = new;
}

/**
 * list_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_add(struct list_head* new, struct list_head* head)
{
    __list_add(new, head, head->next);
}

/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_tail(struct list_head* new, struct list_head* head)
{
    __list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head* prev, struct list_head* next)
{
    next->prev = prev;
    prev->next = next;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void list_del(struct list_head* entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = NULL;
    entry->prev = NULL;
}

/**
 * list_replace - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * If @old was empty, it will be overwritten.
 */
static inline void list_replace(struct list_head* old, struct list_head* new)
{
    new->next       = old->next;
    new->next->prev = new;
    new->prev       = old->prev;
    new->prev->next = new;
}

static inline void list_replace_init(
    struct list_head* old, struct list_head* new)
{
    list_replace(old, new);
    INIT_LIST_HEAD(old);
}
static inline int list_empty(const struct list_head* head);

/**
 * list_move_lists - move all entries of from to list to.
 * @from: of which list entries will be moved from.
 * @to: of which list entries will be moved to.
 */
static inline void list_move_lists(struct list_head* from, struct list_head* to)
{
    if(list_empty(from)) return;

    to->next = from->next;
    to->prev = from->prev;

    from->prev->next = to;
    from->next->prev = to;

    /* set from's prev and next to set list from empty. */
    from->prev = from;
    from->next = from;
}
/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(struct list_head* entry)
{
    __list_del(entry->prev, entry->next);
    INIT_LIST_HEAD(entry);
}

/**
 * list_move - delete from one list and add as another's head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
static inline void list_move(struct list_head* list, struct list_head* head)
{
    __list_del(list->prev, list->next);
    list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
static inline void list_move_tail(
    struct list_head* list, struct list_head* head)
{
    __list_del(list->prev, list->next);
    list_add_tail(list, head);
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(
    const struct list_head* list, const struct list_head* head)
{
    return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const struct list_head* head)
{
    return head->next == head;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @head: the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
static inline int list_empty_careful(const struct list_head* head)
{
    struct list_head* next = head->next;
    return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @head: the head of the list
 */
static inline void list_rotate_left(struct list_head* head)
{
    struct list_head* first;

    if(!list_empty(head)) {
        first = head->next;
        list_move_tail(first, head);
    }
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @head: the list to test.
 */
static inline int list_is_singular(const struct list_head* head)
{
    return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(
    struct list_head* list, struct list_head* head, struct list_head* entry)
{
    struct list_head* new_first = entry->next;
    list->next                  = head->next;
    list->next->prev            = list;
    list->prev                  = entry;
    entry->next                 = list;
    head->next                  = new_first;
    new_first->prev             = head;
}

/**
 * list_cut_position - cut a list into two
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *	and if so we won't cut the list
 *
 * This helper moves the initial part of @head, up to and
 * including @entry, from @head to @list. You should
 * pass on @entry an element you know is on @head. @list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 */
static inline void list_cut_position(
    struct list_head* list, struct list_head* head, struct list_head* entry)
{
    if(list_empty(head)) return;
    if(list_is_singular(head) && (head->next != entry && head != entry)) return;
    if(entry == head)
        INIT_LIST_HEAD(list);
    else
        __list_cut_position(list, head, entry);
}

static inline void __list_splice(const struct list_head* list,
    struct list_head* prev, struct list_head* next)
{
    struct list_head* first = list->next;
    struct list_head* last  = list->prev;

    first->prev = prev;
    prev->next  = first;

    last->next = next;
    next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice(
    const struct list_head* list, struct list_head* head)
{
    if(!list_empty(list)) __list_splice(list, head, head->next);
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice_tail(
    struct list_head* list, struct list_head* head)
{
    if(!list_empty(list)) __list_splice(list, head->prev, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * The list at @list is reinitialised
 */
static inline void list_splice_init(
    struct list_head* list, struct list_head* head)
{
    if(!list_empty(list)) {
        __list_splice(list, head, head->next);
        INIT_LIST_HEAD(list);
    }
}

/**
 * list_splice_tail_init - join two lists and reinitialise the emptied list
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * Each of the lists is a queue.
 * The list at @list is reinitialised
 */
static inline void list_splice_tail_init(
    struct list_head* list, struct list_head* head)
{
    if(!list_empty(list)) {
        __list_splice(list, head->prev, head);
        INIT_LIST_HEAD(list);
    }
}

/**
 * list_entry - get the struct for this entry
 * @ptr:	the &struct list_head pointer.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_struct within the struct.
 */
#define list_entry(ptr, type, member) container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @ptr:	the list head to take the element from.
 * @type:	the type of the struct this is embedded in.
 * @member:	the name of the list_struct within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
    list_entry((ptr)->next, type, member)

/**
 * list_for_each	-	iterate over a list
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
#define list_for_each(pos, head) \
    for(pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev	-	iterate over a list backwards
 * @pos:	the &struct list_head to use as a loop cursor.
 * @head:	the head for your list.
 */
#define list_for_each_prev(pos, head) \
    for(pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_safe(pos, n, head)                  \
    for(pos = (head)->next, n = pos->next; pos != (head); \
        pos = n, n = pos->next)

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal
 * of list entry
 * @pos:	the &struct list_head to use as a loop cursor.
 * @n:		another &struct list_head to use as temporary storage
 * @head:	the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head)             \
    for(pos = (head)->prev, n = pos->prev; pos != (head); \
        pos = n, n = pos->prev)

/**
 * list_for_each_entry	-	iterate over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry(pos, head, member)                \
    for(pos = list_entry((head)->next, typeof(*pos), member); \
        &pos->member != (head);                               \
        pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)        \
    for(pos = list_entry((head)->prev, typeof(*pos), member); \
        &pos->member != (head);                               \
        pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_prepare_entry - prepare a pos entry for use in
 * list_for_each_entry_continue()
 * @pos:	the type * to use as a start point
 * @head:	the head of the list
 * @member:	the name of the list_struct within the struct.
 *
 * Prepares a pos entry for use as a start point in
 * list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
    ((pos) ?: list_entry(head, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member)           \
    for(pos = list_entry(pos->member.next, typeof(*pos), member); \
        &pos->member != (head);                                   \
        pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)   \
    for(pos = list_entry(pos->member.prev, typeof(*pos), member); \
        &pos->member != (head);                                   \
        pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current
 * point
 * @pos:	the type * to use as a loop cursor.
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member) \
    for(; &pos->member != (head);                   \
        pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against
 * removal of list entry
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)            \
    for(pos = list_entry((head)->next, typeof(*pos), member),     \
    n       = list_entry(pos->member.next, typeof(*pos), member); \
        &pos->member != (head);                                   \
        pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against
 * removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member)   \
    for(pos = list_entry(pos->member.next, typeof(*pos), member), \
    n       = list_entry(pos->member.next, typeof(*pos), member); \
        &pos->member != (head);                                   \
        pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe
 * against removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member)     \
    for(n = list_entry(pos->member.next, typeof(*pos), member); \
        &pos->member != (head);                                 \
        pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against
 * removal
 * @pos:	the type * to use as a loop cursor.
 * @n:		another type * to use as temporary storage
 * @head:	the head for your list.
 * @member:	the name of the list_struct within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member)    \
    for(pos = list_entry((head)->prev, typeof(*pos), member),     \
    n       = list_entry(pos->member.prev, typeof(*pos), member); \
        &pos->member != (head);                                   \
        pos = n, n = list_entry(n->member.prev, typeof(*n), member))

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @pos:	the loop cursor used in the list_for_each_entry_safe loop
 * @n:		temporary storage used in list_for_each_entry_safe
 * @member:	the name of the list_struct within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member) \
    n = list_entry(pos->member.next, typeof(*pos), member)

#endif /* _LINUX_LIST_H */
